Exploration of Alkaliphilic Bacteria Alkalitalea saponilacus Identifies Glycoside Hydrolases With Biotechnological Potential

Abstract

Soap Lake, a small meromictic lake in Washington State, USA, harbours a diverse microbial community adapted to high carbonate, sulfate and sulfide concentrations and a pH of approximately 9.8. Alkalitalea saponilacus, an anaerobic obligate bacterium from the lowest layer of Soap Lake, encodes multiple secreted enzymes, bioinformatically annotated as active on a range of carbohydrates. The ability of these enzymes to function under their extreme native conditions offers considerable industrial potential, most notably in the production of granular laundry and automatic dishwashing detergents that require robust performance under highly ionic conditions. Whilst some alkaline-stable enzyme classes exist within current detergent formulations, there is a significant underrepresentation of non-starch polysaccharide-targeting candidates, positioning A. saponilacus as an untapped reservoir for this application. This study investigates A. saponilacus beta-glucan degradation and confirms, using RT-qPCR, the involvement of polysaccharide utilisation loci (PUL) 10 in this process. A representative glycoside hydrolase 16 from this PUL has been heterologously expressed and evaluated as a beta-glucan-targeting candidate, stable under harsh alkaline conditions. To demonstrate the industrial potential of A. saponilacus across both genomic location and functional enzyme families, a mannan-targeting glycoside hydrolase 26 and a cellulose-targeting glycoside hydrolase 9 were also evaluated for substrate deconstruction under high pH conditions. All three model GHs were tested for complex stain removal within a commercial detergent formula, where they exhibited considerable potential as additives. These results reinforce the prospects of the respective molecules, and ultimately the A. saponilacus proteome, for biotechnological applications where performance under alkaline or strongly ionic conditions is required.